T151 Current Trends in Landslide Monitoring: New Techniques, Methods, Successes, Failures, and Case Studies III

Monday, 23 October 2017
1:30 PM - 5:30 PM
Skagit 5

ROCFKALLS AND SMALL PRECURSOR DEFORMATION DETECTED USING OBLIQUE AERIAL SFM PHOTOGRAMMETRY: CASE HISTORY FROM TENNESSEE PASS, CO

Paper number: T151-10
Program: Technical Sessions
Time: 3:45 PM – 4:00 PM

Authors

Abstract

Large rockfalls occurred in April and December 2014, impacting U.S. Route 24 near Tennessee Pass, Colorado. Following these rockfall events, Colorado Department of Transportation (CDOT) commissioned a study to monitor and assess the rockfall source zones.

Oblique aerial photographs of the slope were collected from a moving helicopter on five occasions between April and June 2015. From each oblique aerial photogrammetry (OAP) survey, we generated 3D models and completed 3D quantitative change-detection to determine model differences as small as 5 cm. Analysis showed that a number of small rockfalls and debris slides occurred over the course of the study. Additionally, results suggest that a large ‘cap block’ composed of at least three independent and detached blocks, ranging from 10 m3 to 100 m3, underwent downslope displacements from 5 to 15 cm. OAP change-detection results were validated with a displacement signal from a crackmeter that had been previously installed on the cap block. The OAP change-detection and the crackmeter data were in good agreement at this location, with both showing close to 5 cm of movement over the course of this study. Additional analysis showed that the block accelerated during a three-day precipitation event in early May, which came at the end of a prolonged period of freeze-thaw action.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-295082

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